Rectifier



Nov. 28, 1950 c. A. EscoFFl-:RY

RECTIFIER Filed July 22, 1947 Vf m f R. mf mA. m W W C Patented Nov. 28,1950 lili? Charles A. Escalier-y. East range, N. J., assigner to FederalTelephone and Radio Corporation, New York, N. Y., a corporation ofDelaware Alliicltinn Illy 22, 1947, Serial No. 762,694

l Myinventlonrelatestorectiilersandisparticularly directed to structuralimprovements in rectiilers oi' the dry-plate semi-conductor Wpc. It hasbeen proposed to apph succeslve layers o! base metal, semi-conductingmetal, and counterelectrode to a rod. While such a rod-tape rectiiier.has excellent electrical characteristi, it may be damaged, in certainindustrial applications, by abrasion oi.' the rather thin and fragilelayers oi.' material on the rod. The layers, inrther. may corrodereadily in some atmospheres, while in other cases, the electrical oi'the rectiiler may be impaired by exposure to certain substances, such asmercury or mercury vapor.

One object oi' my invention is to provide improved means ior enclosingand protecting rodtype rectiiiers.

Another obiect is to provide a protecting covering for rod-typerectiiiers which both mechanically and chemically shields the coatedmaterials oi the rectiiier. which is rugged in construction yetrelatively inexpensive, and which is compact and pleasing in appearance.

The scope of my invention is donned with particularity in the appendedclaims and preferred embodiments, which are described in the followingparagraphs and shown in the accom drawing, in which:

Fig. 1 shows in longitudinal section, one rodtype rectiiler of myinvention, and

rigs. 2 and 3 show in elevation. and partly in section. alternativerod-type rectiers of my invention.

The particular rectiiler contemplated here comprises a core rod l,either solid or hollow, with an outside surface composition suitable forthe electrical base oi' semi-conductor materials. For lightness andstrength, aluminum serves well as rod metal, while iron. nickel, orcobalt is desirable as base metal for the semi-conductor. .Accordingly,I recommend an aluminum rod plated with one of the ferrous metals,nickel being easy to deposit electrolytically. The semi-conductormaterial 2 is preferably metallic selenium, which also may beelectro-deposited from suitable electrolytes. One end of the rod isuncoated with the semi-conducting layer so that electrical connectionmay be made to the rod. The semi-conductor is then covered with acounterelectrode layer 3, a low melting alloy being preferred such ascommercial oods metal, or an alloy of cadmium, tin, bismuth, and lead,which has a melting point below the semi-conductor metal.

2 Chilli.. (Cl. 175-366) proportioned as to melt below about 200 degreescentigrade so that it may be applied in the molten state, as by dipping,to selenium without melting the selenium. Selenium melts at about 21'1degrees centigrade.

According to my invention, the ends of the coated rod are enclosed interminal caps I and 5 which electrically contact the base metal and thecounterelectrode, respectively. The caps accordingly comprise the twoelectrical terminals oi' the rectifler, and may conveniently beconnected in circuit by pressing the caps into holders oi' the type usedfor cartridge fuses. Lead wires may of course be soldered or welded tothe caps il' desired. The cap 4 on the uncoated end of the rod issecured in place by tinning the interior of the cap and solderingdirectly to the rod, and the cap 5 on the counterelectrode may becrimped lightly to bind it in place without fracturing the underlyingcoatings.

Finally, the edges of the caps are sealed and the counterelectrode andsemi-conductor layers are covered with a quite heavy protective coating6 of non-conducting paint or enamel. lA resin base thermoplastic may,alternatively, be applied, or any non-porous non-conducting materialwhich will adhere to metal may be used. A still further alternative maycomprise a wrapping oi. thin raw rubber that is vulcanized in place. Theprotective coating contemplated here will not harden and crack or chipwith age but will remain suiiciently plastic to maintain the hermeticseal at the edges of the caps.

The caps may be exteriorly polished or plated with rust resisting metalfor good contacting surfaces, and the protective and sealing coat may beappropriately colored, if desired. to indicate rectifier capacity. Thefinished rectifier is mechanically rugged, is heremetically sealed, ispleasing in appearance, and most important, is relatively inexpensive inconstruction. My recti iler is adapted for manufacture by high-speedautomatic processes, little hand work being re. quired. AThesemi-conducting and counterelec@ trode layer are plated continuously andthe caps. of the inexpensive drawn type, may be rapidly crimped andsoldered in place. Painting and drying can of course be performed on aconveyor.

In Fig. 2, the cap 5 on the coated end of the rod is extended over thecounterelectrode to the edge of the counterelectrode plating and the cap4 on the rod is extended to near the edge oi! the semi-conducting layer.The exposed edges of The constituents of the mentioned alloy are so therod platingg 2 and 3 between the caps are 3 than covered with theprotective and sealing coat i, as in Fig. 1. The coat. in thisembodiment, is a comparatively narrow band of paint or plastic aroundthe rectiiicr.

In applications where a uniform diameter throughout the length oi thereotiiier cylinder is not important, the cap 4 may be omitted assuggested in Fig. 3 and the bared end of the rod I may serve as oneterminal of the`rectiiier. The protective coating 6 seals the rim of thecap I and covers the exposed edges of :the semi-conducting layer 2 andthe counterelectrode' alloy 3. Again, simplicity, hermetic sealing.ruggedness, and neat appearance characterize my novel rec- I claim: n

l. A rectifier comprising a. metal rod, a. semiconducting layer oi'selenium substantially covering said rod, one end only of said rod beingcxposed, a counter-electrode alloy substantially covering saidsemi-conducting layer with the edge only o! said semi-conducting layerbeing exposed. a, metal cap itted over the end ot said rod carrying saidcounterelectrode coating, and a protec- 4 tive insulating coating onsaid rod from the rim of said cap to near the end of the mentionedexposed portion o! the rod.

2. A rectiiler comprising a. rod, successive layers of semi-conductingand counterelectrode materials on said rod and extending from one end tonear the other end of said rod, a deep cap telescoped over said one endand substantially enclosing the counterelectrode layer, and a hermeticseal between the rim of said can and said rod.

CHARLES A. ESCOFFERY.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Italy Feb. 24, 1931

